Today, the terms “sociopath” and “psychopath” are used interchangeably — often as a nice way of avoiding “crazy” — yet in recent years the difference between “psychopath” and “sociopath” has become as widely pronounced as the scientific difference between shell shock and post-traumatic stress disorder, which is to say it’s massive.

Mental illness-speak is rarely politically correct. That guy that lives upstairs is crazy. The driver behind you is a psycho. Your in-laws are nuts. We deploy these charged words effortlessly, lobbing insults that aren’t just incendiary but, medically and culturally speaking, outdated. Psychopaths and sociopaths are among this ilk. While they share many common traits, the parts that differ are critical to understanding their distinction.

Why the Difference Matters

It’s important to keep in mind that mental disorders arise for a number of reasons. Sociopathy, while severely the less understood of the two disorders, can be congenital or acquired. Psychopathy, meanwhile, is generally considered a confluence of genetic and chemical imbalances. Psychopaths lack the proper neurological frameworks to develop a sense of ethics and morality. Sociopaths interact with their social worlds in a meaningful way, but their moral compasses needed a massive tune-up yesterday.

Jack Pemment, graduate student in the University of Mississippi Biology department, believes the differences cannot be understated — for three reasons. First, the term “psychopath” has reached a critical, highly specific definition that scientists widely recognize. Second, science has become increasingly hesitant to use the two terms interchangeably. “And lastly,” he wrote in a report for the journal Aggression and Violent Behavior, “in light of the ﬁrst two reasons, the neurology underlying the psychopath and the sociopath can only be different, a crucial fact to be realized when seeking to understand the etiology, behavioral characteristics, and potential treatments for each.”

In other words, science now understands why the distinction is crucial to properly understanding psychopathy and sociopathy. It’s a distinction that could mean the difference between allocating resources to rehabilitate the person’s mental health and locking them up forever. But what is it?

What is the Difference?

Psychologists tend to break down the two groups by certain factors, and they have a lot in common. Both tend to be charming, despite being unable to empathize normally with others. They offer convincing systems of fear and disgust, but tend to lack both. Here’s the crux, though: Psychopaths cross the line. Sociopaths may hole up in their houses and remove themselves from society, while a psychopath is busy in his basement rigging shackles to his furnace.

Psychopaths are dangerous. They’re violent and cruel, and oftentimes downright sinister. They show no remorse for their actions, usually because of a lesion on a part of their brain responsible for fear and judgment, known as the amygdala. Psychopaths commit crimes in cold blood. They crave control and impulsivity, possess a predatory instinct, and attack proactively rather than as a reaction to confrontation: A 2002 study found that 93.3 percent of the psychopathic homicides were instrumental in nature (meaning they were more or less planned), compared with 48.4 percent of the homicides by people who weren’t psychopaths.

Sociopaths are a different breed. They, too, may suffer from their mental illness as a result of lesioned brain regions. Upbringing may also play a larger role in a child becoming a sociopath versus those that are diagnosed as psychopaths, or the slide into dementia on the other end of the spectrum. Sociopathic behavior is manifested as conniving and deceitful, despite an outward appearance of trustworthiness or sincerity. Sociopaths are often pathological liars. They are manipulative and lack the ability to judge the morality of a situation, but not because they lack a moral compass; rather, their existing moral compass is greatly (yet not always dangerously) skewed. Pemment, for one, says this could point to both a social and neurological component.

“There are neurological correlates for how beliefs could promote specific kinds of attitudinal or behavioral moral outcomes,” he wrote. “These correlates provide a basis for studying how beliefs create our moral integrity by affecting our empathy circuit. However, a large component of sociopathy involves antisocial behavior, and I am unaware of any neurological study that ties beliefs to antisocial behavior.”

This means that while psychopathy and sociopathy both likely involve impaired cognitive function, the two differ in which circuits are affected. Psychopaths are fearless; sociopaths aren’t. Psychopaths don’t have a sense of right and wrong; sociopaths do. But both are equally capable of ruining lives and destroying relationships — not that they care.